Daimy’s

I. Energy Balance of the Earth
A. In the tropics, significantly more energy is absorbed from the sun than is radiated back out to space in the infrared. “Tropics” indicates latitudes of +/- 25 degrees. Here is a region where the Earth is gaining energy in excess of what it is returning to space. In the extra-tropics, latitudes greater than 25 degrees, there is an energy deficit. Less is being absorbed tan is sent back into space. Taken as a whole, the Earth maintains an approximate energy balance: energy absorbed from the sun on a global basis is balanced more or less by energy radiated to space.
1. There are two ways to move energy:
a. Circulation of air; energy from the low latitudes is transported to the high latitudes.
b. The ocean; currents take energy from low latitude to high latitudes.
2. The climate of the Earth is basically determined by the energy imbalance between low latitudes and high latitudes, and the response of air and water to that imbalance. A portion of the energy excess in the tropics is transported to higher latitudes to offset the energy deficit in the extra-tropics. An approximately equal mount is transferred by the ocean.
II. Circulation of Air
A. Warm air rises in the tropics, drawing moisture from the warm oceans. There are three regions of tropics in which the air rises in particular. One is in Indonesia, in the western tropical pacific. The second is over the Amazon basin in South America and the third is in Africa. In other parts of the tropics the air isn’t rising, it’s actually sinking. These are called strong centers of convective activity. Air moves from the equatorial area to higher latitudes at an altitude of 10 km or so above the surface. This is how the warm dry air is moved from one area to another. Tropical air is unable, however, to make it past latitudes of about 30 degrees. Once it gets to this region, it now begins to sink back to the surface. The rotation of the Earth prevents it from rising above 30 degrees latitude and causes it to turn to the east. Eventually, it runs out of momentum toward the poles and sinks back to the surface, setting up a circulation loop known as the Hadley circulation, named in honor of the English meteorologist, George Hadley, who first described this process more than 250 years ago.
1. As it begins its journey at the surface in the tropics, the air contains a relatively large content of water vapor. Water vapor is removed by rain as the air rises. As the air moves to higher latitudes, its moisture content is severely depleted. The sinking portion of the Hadley circulation is responsible for the band of deserts that ring the Earth in the subtropics – the Sahara, for example. It rains where air rises. It is dry and hot where it sinks. When we think about possible climate change, we need to think about the implications for the latitudinal extent of the Hadley circulation. An expansion of deserts to higher latitudes would have important implications for those who live on the margins. For that matter, a retreat would also be significant.
III. Trade winds
A. Trade winds are surface winds that blow from the southeast in the southern hemisphere and from the northeast in the northern hemisphere at a generally reliable clip. This is the return flow of the Hadley circulation.
B. This is how air is exchanged between equatorial regions and mid-latitudes.
IV. Air Circulation at Higher Latitudes
A. We must think of this in terms of summer and sinter. In summer, the Earth is getting a lot of energy from the sun at the higher latitudes, because of the tilt of the axis of the Earth. In the polar circle, for example, the sun is shining 24 hours a day. In winter, however, you have the exact opposite. In these areas, the summer climate is virtually working on its own. In the winter, you don’t have a lot of energy input from the sun, allowing the surface to get really cold. In polar regions it does get cold, but not as cold as it could be, because of the energy supply coming from the atmosphere and the ocean at lower latitudes.
B. There is a relatively sharp transition between warm tropical air and cold high latitude air, especially in winter. This boundary is marked by a stream of high-speed air traveling in a generally west-to-east direction around the Earth. This system is referred to by meteorologists as the jet stream. The velocity of the jet stream is highest at an altitude of several kilometers above the surface in the northern hemisphere. In the high latitude side of the jet stream, the air is cold. On the low latitude side it is warm. The greater the difference in temperature from the warm to cold side, the higher the speed of the jet stream.
1. The jet stream does not always maintain a constant latitude as it flows around the Earth. Occasionally, it can develop a significant meander: it can swing temporarily in a loop to higher latitudes in one region with a compensating loop to lower latitudes elsewhere. Those of us who live in cold winter regions such as Boston have frequently experienced the dramatic impacts of such swings in the jet stream. Temperatures can jump by tens of degrees in a matter of hours as the jet stream migrates from south to north, as a major meander passes overhead. We can go from cold to warm then back to bitter cold in a matter of days.
2. Whether winters are mild or cold depends on where we live relative to the average position of the jet stream.
3. A key question for the future concerns the response of the jet stream to changes in the atmosphere arising as a consequence of the increasing burden of greenhouse gases. In general, we may expect winters to be milder. This may be considered a boon for those who live in regions that are presently cold in winter. But a change in winter climate can have important implications for ecosystems. The type of vegetation that grows in a particular climate. If the nature of this climate regime were to change dramatically and rapidly, natural ecosystems might find it difficult to adjust.
4. The atmosphere is often unstable in the vicinity of the winter jet stream. These instabilities take the form of storms that can spin off and carry air to higher latitudes. Meteorologists refer to these instabilities as eddies. Eddies play a very important role in carrying heat from low latitudes to high latitudes, especially in winter.
V. Jet Stream: Land vs. Sea
A. The ocean maintains relatively the same temperature from day to night or indeed from day to day. This is possible because the wind is churning up 10 to 100 meters of surface water, allowing the heat to be stored in the summer and released in the winter. The ocean is a good way to sore hear.
B. Over the land, the heat that’s absorbed from the sun in the summer is absorbed right at the surface. The continent will heat up during the summer and cool down during the winter. This sets up a very important circulation loop that works like this:
1. During the summer, you are warming up the continent. Air over the continent tends to rise and then sink over the bordering ocean. So you build up high pressure over the ocean and low pressure over the land. This process is reversed in winter.
2. The Indian monsoon is another element of the land/sea circulation. During the monsoonal period the Indian continent warms up and the circulation is generated by the low-pressure system on the Indian subcontinent and the high pressure outside coming from the ocean. As this air comes across the ocean, it picks up moisture and drops rain on the continent. In the winter, the opposite happens.
Conclusion:
1. The total amount of rain is limited by the amount of evaporation that occurs from the world’s oceans. It can’t rain more than it evaporates. The water vapor in the atmosphere doesn’t stay there very long.
2. Evaporation is the result of heating up a body of water, energy driving water from the liquid to the gas phase. Absorption of sunlight on the surface of the world’s oceans plays a major role in determining how much evaporation is going to take place and consequently how much rainfall will occur.
3. We have focused here on the role of the atmosphere in transporting heat from the tropics where the energy balance (the difference between heat absorbed from the sun and infrared radiation emitted back to space) is positive, to higher latitudes, where it is negative.

       For a very long time America has led the world in higher education, quantitatively at least. In addition to 200 of junior colleges with two-year courses, teachers’ colleges and special schools, there are over 2,000 universities, colleges or other such institutions, big and small, public and private, famous and obscure. Rapid development of higher education, a common feature in contemporary societies, is continuing at such a rate that America looks like being far ahead of Europe for a very long time. The growing demand for highly-qualified people, in an ever-more-complex modern society, and the declining opportunities for the less well-qualified, together with the growth in the total numbers of young people caused by the high birth-rate around 1950-1960, brought the total number of students to 10 million by the 1970s. More than a third of all students are women.

       With so great a proportion of the young people entering higher education there is a problem of maintaining academic standards, and the process can be painful. Half of those who embark on higher studies fail to graduate. The number who drop out after one or two years is disturbingly large, though there is evidence that even incomplete university study gives a person better career prospects than none at all. On the other hand, one in five of all who receive bachelors’ degrees, go on to take higher degrees, so the number of people receiving higher degrees each year, representing at least six years’ study at university level, is by now over 100,000.

       All this effort in education is very expensive. Some of the costs come from fees and benefactions, particularly towards research, but most have to be paid from public funds. There is a supposed popular value of education as an investment by society.

       Obviously, with a total of 2,000 universities and colleges there must be great differences in quality and reputation among them. Many have achievements substantial enough for them to be well known all over the world, but among these there are a few which are outstanding in their reputation, both nationally and internationally. These include a few private institutions in various parts, and several of the greatest state universities, but none surpass the group of old private north-eastern universities commonly known as the Ivy League. Of course, the best known of all is Harvard, which is situated in Cambridge, Massachusetts, in the urban area of Boston. Yale founded in 1701, is in New Haven, between Boston and New York. There is much in common between Harvard and Yale, and together they occupy a position in American university life as Oxford and Cambridge in England, so Qinghua and Beijing two universities in China (!@#@$%#$, sweating…).